Cloning and characterization of thermophilic cellulase and its application in the transformation of ginsenosides

Abstract A novel cellulase (BcelFp) was identified from Fervidobaterium pennivorans DSM9078 which had biotransformation activity for PPD-type ginsenosides. Sequence analysis of BcelFp revealed that it could be classified into glycoside hydrolase family 5 (GH5). The gene encoding a 323-amino acid protein was cloned and expressed in Escherichia coli. The recombinant enzyme was purified, and its molecular weight was approximately 37 kDa. The recombinant BcelFp exhibited an optimal activity at 95 oC and pH 5.5 and showed high thermostability. The cellulase had high selectivity for cleaving the outer glucose moiety at the C3 carbon of ginsenoside Rb1, Rb2, Rc and Rd, which produced the more pharmacologically active gypenoside XVII (GypXVII), Compound O (CO), Compound Mc1 (CMc1) and F2, respectively. The Km values for Rb1, Rb2, Rc and Rd were 3.66 ± 0.04 µM, 4.02 ± 0.12 µM, 5.95 ± 0.03 µM, 0.67 ± 0.006 µM, respectively. The kcat/Km value of BcelFp for ginsenoside Rd was 27.91 mM-1s-1, which was much higher than the previously enzymes. This study was the first report of the highly efficient and selective transformation of GypXVII, CO, CMc1 and F2 from Rb1, Rb2, Rc and Rd by a GH5-family thermophilic cellulase.